Many people assume that just by creating an Apple ID, they automatically have an iCloud email address. This is not necessarily the case since people typically use a different email address as their Apple ID.
In order to use an @icloud.com (or @mac.com, @me.com for that matter) email address, you must set that up separately and this is actually a required step if you plan to use iCloud Mail.
So here are the steps to do it from your iOS device:
Go to Settings and go to very top until you see your name and tap on it.
On the next screen, type on iCloud.
Look for Mail under APPS USING ICLOUD and turn it on. If it’s already On, that means you’ve already had and @icloud.com email address.
Once the Mail is On, you see an option to Create it. Just follow the instructions from there.
Once you finished setting it up, you can also use that as your Apple ID email address.